We use an audible click-track/metronome through one of the channels on our GLD-112.
I suggest allowing the FX (tap) tempo, such as for delays, to be triggered by the Gate of an arbitrary click-track channel.
Since every channel already has a Gate that can function as a binary on/off trigger (actually, we just need the “on” trigger) – and the FX engine already supports (tap) tempo… my bet is the processing power required for this is virtually nil.
The user-interface is the only part that would require a bit of thought… But I’m sure your UI/UX designers are up to the challenge 